In national statistics for the United States, including many national surveys on drug use, Americans are divided into four racial groups: (1) white, (2) black, (3) Asian or Pacific Islander, (4) American Indian or Alaska native. The races are often subdivided into ethnic groups. For example, people with recent or distant family origins in such countries as Spain, Portugal, Mexico, and Cuba belong to an ethnic group called Iberian, Hispanic, or Latino. People also belong to cultural groups, which share similar customs, ideas, and behaviors. Racial, ethnic, cultural, and religious backgrounds often overlap.

The use of drugs and alcohol differs from one ethnic, cultural, or religious group to another. Drug abuse, as well as the way in which people respond to treatment, also varies within groups. It is helpful for public health officials to...